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Extension Pork Industry Handbook, no. 047 (no date)

Page 001

HERD HEALTH
PIH-47
pork
industry
handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Transmissible Gastroenteritis (TGE)
Authors
E. O. Haelterman, Purdue University
E. H. Bohl, Ohio State University, O.A.R.D.C., Wooster, Ohio
Reviewers
Lawrence Morehouse, University of Missouri
Charles Andrews, Washington Court House, Ohio
Ritchie Jordan, Suffolk, Virginia
Among the diarrheal diseases of baby pigs, transmissible gastroenteritis (TGE) is the most deadly and the most feared by swine men. Accurate statistics are not available, but extensive epidemics of TGE occur every winter in the Swine Belt. When the disease strikes a herd during a concentrated farrowing period it is not unusual to lose most of the pigs farrowed over the next two to three weeks.
Clinical Signs—Appearance
TGE is usually a mild disease except in pigs less than about 3 weeks of age and in sows that sicken at or near farrowing. Pigs other than these have a more or less fluid diarrhea for 1 to a few days, and vomiting is occasionally observed. They may not gain, or may actually lose, weight for a week or so, but in most cases they make up these losses later.
The signs in newborn pigs are much more severe. Diarrhea starts 18-30 hours after the pig is exposed to virus. Thus, pigs born in a farrowing house in which a TGE outbreak is going on are born healthy and show the first signs of TGE on the day following birth. Diarrhea that sometimes occurs in pigs during the first hours of life is not TGE.
The first sign seen in baby pigs that are carefully watched is almost always vomiting. This may be missed in pigs housed in pens in which the sows run loose, because they will eat the vomitus. Vomiting is followed very quickly by diarrhea. The first diarrhea, again, can be missed by a casual observer because it is very thin and watery; it runs down the hind legs and drips from the tail. As the disease progresses, it becomes more obvious. The diarrhea thickens, becomes yellowish and is seen in little puddles on the floor.
The pigs are dehydrated, their ears lie back, their eyes are sunken, they are thirsty and will drink water or attempt to suckle even though they become progressively weaker.
Most pigs that die of TGE do so in 3-5 days after they are infected, but in some herds deaths may occur earlier. Pigs that have TGE are highly sensitive to chilling, and this may be at least a partial explanation for the rapid deaths sometimes seen. Pigs that live more than 5-6 days will usually recover. In most cases these pigs will do well, but in some herds there may be pigs that never make satisfactory gains thereafter.
Sows that sicken just before or just after farrowing become feverish, they often vomit, refuse feed and have a greenish diarrhea that persists for 1 to a few days. Their milk quantity diminishes and they may even dry up, but in most cases if the litter continues to suckle they will return to normal lactation.
The Cause
TGE is caused by a virus that belongs to the group called coronaviruses. They have projections on their surfaces that appear in electron micrographs like sunflower petals. The virus has an envelope that is easily destroyed by detergents, and it is readily inactivated by warm temperatures, drying, and sunlight. The virus is resistant to acid—this allows it to pass through the stomach and infect the small intestine. It survives for long periods in a cold, dark environment and almost indefinitely when frozen.
How the Virus Causes Disease
TGE virus has a special affinity for the cells that line the small intestine. These cells cover millions of tiny villi that project into the intestine to provide a huge surface that functions to digest and absorb nutrients from ingested food (Fig. 1). When TGE virus enters these cells it multiplies and, in the process, kills the cell. This process takes 4-5 hours. When the cell is killed, thousands of virus particles are released to infect other cells on other villi. After 4-5 cycles of virus multiplication almost all of the digestive cells in a
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age or handicap.

HERD HEALTH
PIH-47
pork
industry
handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Transmissible Gastroenteritis (TGE)
Authors
E. O. Haelterman, Purdue University
E. H. Bohl, Ohio State University, O.A.R.D.C., Wooster, Ohio
Reviewers
Lawrence Morehouse, University of Missouri
Charles Andrews, Washington Court House, Ohio
Ritchie Jordan, Suffolk, Virginia
Among the diarrheal diseases of baby pigs, transmissible gastroenteritis (TGE) is the most deadly and the most feared by swine men. Accurate statistics are not available, but extensive epidemics of TGE occur every winter in the Swine Belt. When the disease strikes a herd during a concentrated farrowing period it is not unusual to lose most of the pigs farrowed over the next two to three weeks.
Clinical Signs—Appearance
TGE is usually a mild disease except in pigs less than about 3 weeks of age and in sows that sicken at or near farrowing. Pigs other than these have a more or less fluid diarrhea for 1 to a few days, and vomiting is occasionally observed. They may not gain, or may actually lose, weight for a week or so, but in most cases they make up these losses later.
The signs in newborn pigs are much more severe. Diarrhea starts 18-30 hours after the pig is exposed to virus. Thus, pigs born in a farrowing house in which a TGE outbreak is going on are born healthy and show the first signs of TGE on the day following birth. Diarrhea that sometimes occurs in pigs during the first hours of life is not TGE.
The first sign seen in baby pigs that are carefully watched is almost always vomiting. This may be missed in pigs housed in pens in which the sows run loose, because they will eat the vomitus. Vomiting is followed very quickly by diarrhea. The first diarrhea, again, can be missed by a casual observer because it is very thin and watery; it runs down the hind legs and drips from the tail. As the disease progresses, it becomes more obvious. The diarrhea thickens, becomes yellowish and is seen in little puddles on the floor.
The pigs are dehydrated, their ears lie back, their eyes are sunken, they are thirsty and will drink water or attempt to suckle even though they become progressively weaker.
Most pigs that die of TGE do so in 3-5 days after they are infected, but in some herds deaths may occur earlier. Pigs that have TGE are highly sensitive to chilling, and this may be at least a partial explanation for the rapid deaths sometimes seen. Pigs that live more than 5-6 days will usually recover. In most cases these pigs will do well, but in some herds there may be pigs that never make satisfactory gains thereafter.
Sows that sicken just before or just after farrowing become feverish, they often vomit, refuse feed and have a greenish diarrhea that persists for 1 to a few days. Their milk quantity diminishes and they may even dry up, but in most cases if the litter continues to suckle they will return to normal lactation.
The Cause
TGE is caused by a virus that belongs to the group called coronaviruses. They have projections on their surfaces that appear in electron micrographs like sunflower petals. The virus has an envelope that is easily destroyed by detergents, and it is readily inactivated by warm temperatures, drying, and sunlight. The virus is resistant to acid—this allows it to pass through the stomach and infect the small intestine. It survives for long periods in a cold, dark environment and almost indefinitely when frozen.
How the Virus Causes Disease
TGE virus has a special affinity for the cells that line the small intestine. These cells cover millions of tiny villi that project into the intestine to provide a huge surface that functions to digest and absorb nutrients from ingested food (Fig. 1). When TGE virus enters these cells it multiplies and, in the process, kills the cell. This process takes 4-5 hours. When the cell is killed, thousands of virus particles are released to infect other cells on other villi. After 4-5 cycles of virus multiplication almost all of the digestive cells in a
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age or handicap.